Apparatus for forming multi-phase strip from particle and powder mixture

ABSTRACT

An article or strip formed by compacting coarse metal particles or a mixture of coarse metal particles and a fine powder. The invention is particularly directed to the formation of multiphase strip having a matrix formed of compacted coarse metal particles and at least one second phase formed of a compacted powder. The apparatus and process of forming the strip are also part of the invention. The particles have a diameter of 150 to 1,200 microns and, preferably, have a length-to-diameter ratio of 3:1 to 10:1. The powder material has a diameter of less than 50 microns. Particle size and density segregation effects are minimized by adding powder to the particles at a point in close proximity to the compacting means. The invention is particularly applicable to copper and copper base alloys and is uniquely suited to produce anode matrix combinations in accordance with U.S. Pat. No. 3,574,081.

United States Patent 1191 Horn et a1.

[5 APPARATUS FoR FORMING a MULTI-PHASE STRIP FROM PARTICLE AND POWDER MIXTURE [75] Inventors: Werner G. Horn, Cheshire; Robert M. Neumann, New Haven, both of Conn.

[73] Assignee: Olin Corporation, New Haven,

Conn.

[22] Filed: June 16, 1972 [21] Appl. No; 263,607

Related U.S. Application Data [62] Division of Ser. No. 137,489, April 26, 1971, Pat.

I No. 3,713,474.

[52] U.S.Cl 425/78, 425/363, 425/421 [51] Int. Cl 1322f 3/00 [58] Field of Search 425/78, 405, 11, 355, 363, 425/335 [56] References Cited UNITED STATES PATENTS 2,393,130 l/1946 Toulmin, .lr. 425/78 X 2,514,616 7/1950 Adams 425/78 2,670,516 3/1954 McEachran... '425/421 3,060,540 10/1962 Lapidus 425/421 X 3.165,570 1/1965 Deutsch 425/73 x [111 3,819,311 1 June 25, 1974 l/1968 l-libbing 425/355 Primary Examiner-Robert L. Spicer, Jr. Attorney, Agent, or Firm-Robert l-l. Bachman 1 ABSTRACT An article or strip formed by compacting coarse metal particles or a mixture of coarse metal particles and a fine powder. The invention is particularly directed to the formation of multi-phase strip having a matrix formed of compacted coarse metal particles and at least one second phase formed of a compacted powder. The apparatus and process of forming the strip are also part of the invention. The particles have a diameter of 150 to 1,200 microns and, preferably, have a length-to-diameter ratio of 3:1 to 10:1. The powder material has a diameter of less than 50 microns. Particle size and density segregation effects are minimized by adding powder to the particles at a point in close proximity to the compacting means. The invention is particularly applicable to copper and copper base alloys and is uniquely suited to produce anode matrix combinations in accordance with U.S. Pat. No. 3,574,081.

12 Claims, 6 Drawing Figures APPARATUS FOR FORMING MULTI-PHASE STRIP FROM PARTICLE AND POWDER MIXTURE RELATED U.S. APPLICATION This is a division of application Ser. No. 137,489, now US. Pat. No. 3,773,474, filed Apr. 26, 1971.

BACKGROUND OF THE INVENTION This invention is directed to the formation of articles or strip by compacting coarse particles or a mixture of coarse particles and fine powder. More particularly, the invention is directed to the formation of multiphase strip having amatrix formed of compacted coarse particles'and at least one other phase formed of a compacted powder. The apparatus and process of forming the stripare also part of the invention.

It is known to form strip by hot compacting coarse particles of metals-such as aluminum, magnesium, steel and nickel. It is also known to form strip by compacting powders of such metals.

However, the prior art has not compacted coarse metal particles of copper nor has it ever compacted mixtures of coarse metal particles and at least one fine powderv second phase which are the essential aspects of this invention.

' Strip made from metal powders or mixtures of metal powders cannot be formed at a rapid rate because of the poor flow characteristics of the metal powders. Strips made from coarse metal particles or mixtures of coarse metal particles overcome the poor flow characteristics of the fine metal powders; however, it is not possible to have a uniform dispersion of a fine second phasein the matrix because the second phase particles are very coarse.

The concept of compacting mixtures of coarse metal particles and fine powder was not considered workable because of the inherent particle size and density segregation effects due to the vast difference in size between the coarse matrix particles and the fine second phase powder.

SUMMARY OF THE INVENTION In accordance with this invention, however, a process and apparatus has been developed wherein the powder phase or phases are added to the metal particles just before the mixture is compacted into strip. By so adding the metal powder to the metal particles, particle size and density segregation effects are substantially eliminated.

It is accordingly an object of this invention to provide multi-phase article such as strip having a matrix formed of compacted coarse metal particles and at least one second phase dispersed within the matrix formed of a fine'powd'er.

It is a further object of this invention to provide a strip as above, wherein the matrix particles are copper or a copper base alloy.

It is a further object of this invention to provide strip formed by compacting coarse particles of copper or a copper base alloy.

It is a further object of this invention to provide an apparatus and process for compacting coarse particles of copper and copper base alloy into a densified strip.

It is a further object of this invention to provide a process and apparatus for compacting a mixture of to those skilled in the art from the following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an apparatus suitable for carrying out the process of this invention.

FIG. 2 shows coarse metal particles exemplary of those useful with this invention.

FIG. 3 shows microstructures which illustrate the effect of compacting temperature when hot compacting coarse copper particles into strip.

DESCRIPTION OF PREFERRED EMBODIMENTS The compacting process which must be followed in accordance with this invention when forming coarse metal particles into strip or when forming multi-phase metal strip from mixtures of coarse particles and fine powder is similar to the process of US. Pat. No. 3,076,706, granted Feb. 5, 1963. The process disclosed therein relates to a method of making a solid strip of aluminous metal from preheated coarse particles by roll compacting. The process is clearly distinguishable from the process of the instant invention since'there is no suggestion of compacting mixtures of coarse metal particles and another material in the form of a fine powder to form a multi-phase strip.

US. Pat. No. 3,290,145, granted Dec. 6, 1966 and US. Pat. No. 3,413,101, granted Nov. 26, 1968 disclose the formation of multi-phase strip solely from coarse particles of aluminum and a different material or coarse particles of the different aluminum alloys. The process of these patents are also distinguishable by the absence of any suggestion of compacting mixtures of coarse metal particles and fine powders.

In accordance with the instant invention, coarse particles of a first metal are mixed with a fine powder of a second metal or other material. The mixture is then compacted to a densified strip comprising a matrix formed from the coarse metal particles and at least one highly dispersed fine second phase formed from the metal powder.

The process of the instant invention is particularly applicable to the formation of multi-phase strip in accordance with the teachings of US. Pat. No. 3,574,081, granted Apr. 6, 1971, by M. J. Pryor, assigned to the assignee of the instant invention. The process of the instant invention permits the preparation of any desired anode matrix combination as will be exemplified hereinafter.

Previously known methods of processing strip from metal powders employ relatively fine powders generally less than 50 microns in diameter. The powders are roll compacted into a green strip which is subsequently put through a multi-step sequence of sintering and cold rolling to final gage. Due to the relatively poor flow characteristics of these powders, the rolling speed is usually limited to approximately 10 feet per minute. The present invention in contrast thereto involves the compacting of coarse metal particles, preferably, elongated coarse particles mixed with at least one fine powder second phase to a fully densified strip. Due to the better flow properties of the particles, particularly, the elongated variety as compared to all powder mixtures, higher rolling speeds up to 200 feet per minute can be obtained. If the particles are preheated, no separate or additional sintering or rolling operations are necessary but they can subsequently be performed for gage or temper control or other desired purpose.

In accordance with this invention, for anode matrix combinations covered by US. Pat. No. 3,594,081, it is desirable to restrict interactions between the phases of the strip and, therefore, the strip is preferably processed by hot compaction without any thermal post treatment except perhaps for a flash anneal.

The process will now be described in detail with reference to FIG. 1 which shows a schematic view of a typical apparatus 1 useful for carrying out the processv of this invention by the preferred method of hot compaction. A supply of metal particles 2 is held in hopper 3. The particles 2 are transferred continuously from the hopper 3 by means of vibrators G and shoot 4 into a rotary inconel tube 5 positioned inside a furnace 6 inclined about to the horizontal. The degree of incline is not a critical aspect of this invention and may be set as desired to obtain appropriate flow rates of the particles through the furnace 6. The rotary inconel tube 5 is rotated by conventional means such as drive means 7 connected to the motor 8.

The particles 2 during their stay in the furnace 6 and throughout the operation thereafter, until they have been compacted, are preferably maintained under a controlled gas atmosphere such as a reducing atmosphere. An atmosphere containing 96 volume percent nigrogen and 4 volume percent hydrogen has been found to be highly suitable for this purpose, and is supplied at G.

The rotation of the inconel tube 5 causes the particles 2 to pass through the furnace 6 where they are heated to the desired temperature, preferably, above their recrystallization temperature. The particles 2 are discharged into a feeder box 9 and fall vertically into the nip of a pair of horizontally disposed rolls 10. The feeder box 9 is connected by a gas tight seal at 11 to the rotary tube 5 and is positioned above the horizontally disposed rolls 10. I

To obtain more even distribution of the particles 2 over the area of the roll bite 12, a baffle 13 is preferably employed. The baffle 13 is generally located under the exit 14 of the rotary tube 5.

Gas burners 15 are preferably employed at the end of the rotary tube 5 which emerges from the furnace 6 to keep the particles therein from losing heat. Gas burners 16 are preferably arranged under both rolls to preheat the roll surface to a temperature of 150 to 250C and, preferably, l70 to 200C to reduce the chilling effect of the rolls as they contact the particles.

The second phase powder 17 is preferably added to the preheated matrix particles 2 just before they enter the roll bite 12. It has been found that blending of the two components 2 and 17 at an earlier stage in the process results in severe segregation problems because of the major difference in their particle sizes. Therefore, means are provided to distribute the second phase powder 17 into the preheated matrix particles 2. The second phase powder preferably is added cold.

FIG. 1 shows one possible approach that can be used but it is not meant to be limitive of this invention.

As shown in FIG. 1, the fine powder 17 is sievevibrated from a container 18 located inside the feeder box 9 just above the roll bite 12. The means 19 for vibrating the container 18 is located outside the feeder box 9 and a rod 20 connected to the vibration means 19 and the powder container 18 transmits the necessary vibrational energy. The feed rate can be adjusted by altering the ampliture of the vibrations.

Other means for adding the second phase powders could employ spraying techniques or other known methods of distributing powders. It is merely essential that the powder be added immediately before the mixture enters the roll bite. The fully compacted strip S is guided for further processing and/or coiling by means of a ramp R.

The strip in accordance with the instant invention can be formed at speeds up to 200 feet per minute and perhaps higher; however, preferably, the strip is formed between about 20 and 150 feet per minute.

The coarse particles which form the matrix phase of the composite in accordance with this invention generally have diameters of about 150 to 1,200 microns and, preferably about 300 to 700 microns. Preferably, the particles have a length-to-diameter ratio of about 3:1 to 10:1 and, more preferably, about 4:1 to 6:1.

Various types of metal particles or granules which could be used in accordance with this invention are known in the art. FIG. 2 illustrates three exemplary types of copper particles which were tested for use with this invention. FIG. 2a shows a magnified view (6.5X) of copper particles prepared by chopping scrap electrical wire. Since the wire was chopped in the annealed condition, the particles assume a hook type shape as shown. Most of the particles shown in FIG. 2a range between about 700 to 1,200 microns in diameter.

FIG. 2b shows a magnified view (6.5X) of particles of copper formed in a manner similar to the particles of FIG. 2a; however, the particles were chopped from a finer wire and the bulk of the particles shown range between 400 and 700 microns in diameter.

FIG. 2c shows a magnified view (6.5X) of particles of electrical conductor grade copper wire of three diameters: 320 microns, 450 microns and 510 microns. The wire varied from quarter hard to spring temper and was cut to produce substantially straight particles having approximately a l0:l length-to-diameter ratio.

Before proceeding further, the particles of FIG. 2 were cleaned and annealed in accordance with the practices well known in the art. These steps are not essential to the process and form no part of the instant invention. The need for cleaning and annealing is generally dependent on the prior processing of the particles. In this example the particles were soaked in benzine and rinsed in acetone to assure a surface free from any residue.

The particles were subsequently annealed for 2 hours at 650C under a reducing atmosphere to remove the surface oxides and to assure their ductility. All of the particles shown in FIG. 2 can be successfully processed into a fully densified strip.

The mechanical and electrical properties of the resulting strip as compared to wrought copper alloy strip are shown in Table l.

Tensile Properties Type of Approx. Y.S. 0.1% ksi U.T.S. ksi

Elong. 2"

Minimum Bend Radius. in.

0 to R.D.

90 to R.D. Hardness Electrical Maternal Particl e Vickers Conductivity I Temp. C %IACS Copper 375 20.7 37.7 8.0 4/64 0.008 67.0 101 Particles FIG.

Copper 375 l 1.2 33.8 44.5 0.008 0.008 67.0 101 Particles FIG.

Copper 375 16.2 37.5 36.0 0.008 0.008 75.0 101 Particles FIG.

Annealed 7.5 34.0 44.0 0.008 0.008 62.0 101 Alloy ll0 Strip As shown therein, the finer particles of FIGS. 2b and 2c resulting in strip with mechanical properties comparable to copper alloy 110. The coarser particles of FIG. 2a yielded strip having poorer tensile elongation and bend properties. Therefore, it is preferred to use particleshaving a diameter ranging between about 300 to 700 microns and further, to use substantially straight elongated particles because of their better flow properties. Bent particles have a stronger tendency to interlock and to accumulate in the roll bite, therefore, tending to upset the balance of the metal head required. The better flow properties of straight or slightly bent particles as in FIGS. 2b or 2c versus the hook type particles of FIG. 2a is advantageous for the attainment of higher roll speeds.

When hot compacting the particles, the temperature at which the particles are compacted into strip has been found to be a critical aspect of this invention. Preferably, the temperature should exceed the recrysta1lization temperature of the metal particles. FIG. 3a shows a microstructure magnified 1,000X of a roll compacted strip formed from out wire copper particles wherein the'particles were preheated to 200C prior to compacting. The arrow shows the presence of a continuous oxide interface at the original particle surface. It has been found that copper strip compacted at temperatures between 200 and 250C exhibited very limited strength and bending capability.

FIG. 3b shows a roll compacted strip compacted at a temperature of 375C. Note that the residual oxide interface shown by the arrow is now discontinuous with the result that the strip obtains high properties as shown in Table I.

Therefore, in accordance with the preferred embodiment of this invention, the particles prior to compacting are heated to a room temperature in excess of their recrystallization temperature. For copper or copper base alloys, the temperature at the roll bite is 350 to 500C and, preferably, 375 to 450C.

The microstructure studies in FIG. 3 show that for copper a continuous oxide film acts as a barrier to bonding and restricts recrystallization which occurs in the compacted strip. Therefore, a protective or reducing atmosphere is preferred to prevent oxide build up during the preheat cycle. A thin oxide film, however, below 300 angstroms for copper particles will break up and spherodize during compacting and will not restrict recrystallization and grain growth. The thickness of the oxide film which can be tolerated varies with particle composition.

The examples which follow illustrate the formation of multi-phase strip formed by compacting preheated mixtures of coarse metal particles and a fine powder second phase. The coarse metal particles range in diameter from 300 to 1,200 microns and have a lengthto-diameter ratio of 3:1 to 10:1 and the fine powder second phase has a diameter less than 50 microns and preferably 1-45 microns.

EXAMPLE I Copper particles having a diameter of 400 to 700 microns and a length-todiameter ratio of 3:1 to 6:] were employed using the apparatus of FIG. 1. The copper particles were preheated to a temperature of at least 375C. About 0.5 weight percent of a fine aluminum powder, less than 44 microns in diameter was sievevibrated into the copper particles preheated to 375C just before the roll bite. The compacted sheet had a clean structure with a well dispersed fine second phase. Microscopic examination did not show any interaction between the copper and aluminum resulting from the bonding operation. The resulting strip was exposed to a 3.4 percent sodium chloride solution which was cycled between room temperature and its boiling point for a period of one month. It was found that copper corrosion was almost entirely inhibited and the specimen was covered by a dense and evidently protective film of hydrated aluminum oxide.

EXAMPLE 11 Iron particles about 500 microns in diameter and with a length-to-diameter ratio of 10:1 were preheated to a temperature of 500C and about 0.5 weight perforce less alumina was built up as a film on the specimen.

EXAMPLE III A multi-phase copper strip was processed having a composition similar to known iron containing copper alloys. Elongated copper particles 300 microns in diameter with about a :1 length-to-diameter ratio were preheated to at least 400C. Iron powder 5 microns in diameter was sieve-vibrated into the preheated copper particles in the amount of 0.5 weight percent iron and the mixture was compacted into strip as in the previous examples. The resulting strip was found to have a uniform dispersion of fine iron particles and a copper matrix similar to the known copper alloys.

EXAMPLE IV Multi-phase copper strip was also prepared as in Example I and III with the exception that the second phase powder was graphite, lead or molybdenum disulfide having a diameter less than 50 microns. The resulting strip had a structure similar to conventionally processed material formed by casting or powder metallurgy and can be utilized in self-lubricating applications such as for bearings.

EXAMPLE V Another group of copper matrix strip was prepared by adding powder less than 50 microns in diameter of alumina, barium sulfate, aluminum silicates or silicon carbide. The copper particles were 150 microns in diameter and had about a 6:1 length-to-diameter ratio. One to two volume percent of the second phase powder about 13 to 26 microns in diameter were hot compacted as in the previous examples. The resulting strips have particluar use in frictional and wear resistant applications since they maintain a high coefficient of friction and the thermal energy generated is displaced readily due to the high thermal conductivity of the matrix material.

The process of the instant invention can utilize the techniques of US. Pat. Nos. 3,533,782, granted Oct. 13, 1970 and 3,539,405, granted Nov. 10, 1970, whereby the metal particles are formed by atomizing a metal melt to form droplets which solidify into particles and the particles are compacted before they have been substantially reduced in temperature thereby eliminating an intermediate heating step.

Further, the process of the instant invention is also adapted to form composite strip comprising a backing member and a strip from particle layer as in U.S. Pat. Nos. 2,815,567, granted Dec. 10, 1957 and 3,145,560, granted July 28, 1964.

The particular settings for the roll gap will vary with the type of rolling mill employed and are conventional in the art and do not form part of the instant invention. The previous examples were carried out using a Stanat mill having 6 inch diameter rolls horizontally disposed. For such a mill, the roll gap settings were found to lie between 0.020 inch and 0.100 inch which yielded strip gages between 0.040 inch and 0.070 inch.

The strip in accordance with this invention is preferably compacted to at least a 99.5 percent density.

While the examples illustrate two phase systems, it is possible by this process to incorporate a plurality of phases greater than two. The quantity of the at least one other phase is dictated by the use to which the article is to be put, but is preferably 0.1 to volume percent and more preferably, 0.2 to 3 volume percent. For anode matrix combinations, such as described in US. Pat. No. 3,574,081, it is preferred to use 0.1 to 4.0 weight percent of the at least one other phase.

While the invention has been described with reference to the formation of strip type articles, it is equally applicable to the formation of other types of articles, such as bar, structural shapes and any other shape which is amenable to a continuous hot compacting process. The use of horizontally disposed rolls for hot compacting is not essential to this invention and any desired roll configuration or compacting means could be employed as are well known in the art. One other such compacting means which might prove suitable would be the use of a rotary swaging machine in place of the rolling mill.

The metal particles useful with this invention for forming multi-phase articles may be any of the known metals and their alloys which have the necessary ductility to be compacted into a densified article, for example, iron, aluminum, magnesium, nickel, cobalt and particularly copper.

The second phase powder may be any desired material, for example, metals, ceramics, carbides, insulators, glasses, etc. The powder need not be ductile.

While the invention has been described in detail with reference to the preferred method comprising compacting preheated particles, it is also applicable to other methods of compacting as are known in the art such as compacting followed by sintering. Further, while elongated particles are preferred in accordance with this invention because they provide the best flow properties, particles of any desired shape or mixtures with elongated particles can be used.

It is to be understood that the invention is not limited to the illustrations described and shown herein, which are deemed to be merely illustrative of the best modes of carrying out the invention, and which are suitable of modification of form, size, arrangement of parts and details of operation. The invention rather is intended to encompass all such modifications which are within its spirit and scope as defined by the claims.

What is claimed is:

1. An apparatus for forming a multi-phase article from mixtures of metal particles having a diameter of about microns to 1,200 microns and at least one powder material having a diameter of less than 50 microns, said apparatus comprising:

means for supplying said particles;

means communicating with said particle supply means for compacting said particles into a densified article, including a plurality of parallel rollers; and means intermediate said particle supply means and said compacting means for intermixing said powder with said particles, said intermixing means being located in close proximity to said compacting means. 2. An apparatus for forming a multi-phase article from mixtures of metal particles having a diameter of about 150 microns to 1,200 microns and at least one powder material having a diameter of less than 50 microns, said apparatus comprising:

means for supplying said particles; means for communicating with said particle supply means for preheating said particles to a temperature above their recrystallization temperature;

roller means communicating with said preheating means for compacting said particles into a densified article; and

means intermediate said preheating means and said compacting means for intermixing said powder with said particles.

3. An apparatus as in claim 2 wherein said means for intermixing said powder with said particles comprises a sieve-type container and means for vibrating said container whereby the feed rate can be adjusted by altering the amplitude of the containers vibrations.

4. An apparatus as in claim 3 further including a feeder box located intermediate said preheating means and said compacting means, said intermixing means being located at least in part within said feeder box.

5. An apparatus as in claim 4 wherein said vibrating means is located outside said feeder box and is connected to said container by a member which transmits the necessary vibrational energy to said container.

6. An apparatus as in claim 5 wherein said article comprises a strip, and wherein said means for supplying said particles comprises a vibrating hopper and chute, and wherein said means for preheating said particles comprises a rotary tube through which said particles travel and means located about said tube for heating said tube and the particles within it.

7. An apparatus as in claim 6 further including means for maintaining said particles and said mixture of particles and powder under a controlled gas atmosphere.

8. An apparatus as in claim 7 wherein said controlled gas atmosphere comprises a reducing atmosphere.

9. An apparatus as in claim 7 further including means for heating the faces of said horizontally disposed rolls.

uting means comprises a baffle. 

2. An apparatus for forming a multi-phase article from mixtures of metal particles having a diameter of about 150 microns to 1, 200 microns and at least one powder material having a diameter of less than 50 microns, said apparatus comprising: means for supplying said particles; means for communicating with said particle supply means for preheating said particles to a temperature above their recrystallization temperature; roller means communicating with said preheating means for compacting said particles into a densified article; and means intermediate said preheating means and said compacting means for intermixing said powder with said particles.
 3. An apparatus as in claim 2 wherein said means for intermixing said powder with said particles comprises a sieve-type container and means for vibrating said container whereby the feed rate can be adjusted by altering the amplitude of the containers vibrations.
 4. An apparatus as in claim 3 further including a feeder box located intermediate said preheating means and said compacting means, said intermixing means being located at least in part within said feeder box.
 5. An apparatus as in claim 4 wherein said vibrating means is located outside said feeder box and is connected to said container by a member which transmits the necessary vibrational energy to said container.
 6. An apparatus as in claim 5 wherein said article comprises a strip, and wherein said means for supplying said particles comprises a vibrating hopper and chute, and wherein said means for preheating said particles comprises a rotary tube through which said particles travel and means located about said tube for heating said tube and the particles within it.
 7. An apparatus as in claim 6 further including means for maintaining said particles and said mixture of particles and powder under a controlled gas atmosphere.
 8. An apparatus as in claim 7 wherein said controlled gas atmosphere comprises a reducing atmosphere.
 9. An apparatus as in claim 7 further including means for heating the faces of said horizontally disposed rolls.
 10. An apparatus as in claim 9 wherein said feeder box is maintained in a gas tight relationship with said rotary tube and said rotary tube is maintained in a gas tight relationship with said particle supply means.
 11. An apparatus as in claim 10 further including means located within said feeder box for distributing said particles evenly along the roll bite.
 12. An apparatus as in claim 11 wherein said distributing means comprises a baffle. 